After completion of assembly of a refrigerant system and a refrigerator cabinet of a household refrigerator, it is necessary to test the refrigerant system to insure that it is operable. Testing of the refrigerant system has previously been accomplished by running the compressor of the refrigerant system for a time period sufficient to establish evaporator flooding, which is when liquid refrigerant is converting to gas within that portion of the refrigerant system. At the end of this time period, the temperature at the entrance to the first coil of the serially connected coils of the evaporator has been measured. If the measured temperature is low enough such as 0.degree. F., for example, the refrigerant system is deemed to be operable.
However, this test has occasionally permitted a defective refrigerant system to be deemed operable even though the temperature at the entrance to the first evaporator coil has been sufficiently low to indicate that the refrigerant system is functioning properly. It has been determined that this is because there is not sufficient mass of the refrigerant flowing through the evaporator coils although there has been sufficient mass flow to enable the temperature at the entrance of the first of the evaporator coils to have the required low temperature. This insufficient mass flow can be due to a restriction in the system to flow of the refrigerant, a defective compressor (e.g., a low capacity compressor), a low refrigerant charge, or a high oil charge. A high refrigerant charge or no oil also can cause a defective refrigerant system.
To avoid this problem of a defective refrigerant system being deemed operable, the method of this invention contemplates measuring the temperature of a coil of the evaporator remote from the entrance to the first coil of the evaporator. By determining the temperature of an evaporator coil remote from the first evaporator coil, a defective refrigerant system will not be passed as satisfactory. This is because an evaporator coil remote from the first evaporator coil will not produce the desired temperature if the refrigerant system is defective because of a restriction in the refrigerant system, an incorrect charge of refrigerant or oil in the refrigerant system, or a defective compressor. Experience has shown that a household refrigerator will almost certainly function properly when correct temperatures are produced about one-third to two-thirds of the length of an evaporator from its entrance during an abbreviated test.
When the refrigerant system includes a rotary compressor, it has been determined that it is necessary to activate the refrigerant system for a period of time in excess of forty-five minutes to enable measurement of the temperature in an evaporator coil sufficiently distant from the first evaporator coil to insure that the refrigerant system is operable when the temperature of the specific coil reaches a predetermined temperature of at least 0.degree. F., for example. This relatively long period of time for testing each refrigerant system would significantly reduce productivity of household refrigerators in that the remainder of the manufacturing line could not operate any quicker. Therefore, it is desired that testing of the operability of a refrigerant system be completed in a minimum period of assembly line time.
In one assembly line, it has been determined that testing of the operability of a refrigerant system must be accomplished within twenty-eight minutes. Otherwise, the production line would have to be slowed so that the economics of the production of household refrigerators would be significantly affected.
The method of the present invention satisfactorily solves the foregoing problems by testing a refrigerant system of a household refrigerator within a specific time period of twenty-eight minutes while still being able to measure the temperature of an evaporator coil remote from the first evaporator coil. Applicants have determined that measuring the temperature of the twenty-eight coil will insure that the refrigerant system is operable while still being able to complete the test within the predetermined period of time.